A little F-15C AFM update - 7 December 2013
We've been hard at work on the new advanced flight model for the F-15C and each day we are getting a little closer. Unlike past AFM projects, this one has been a little different because of the characteristics of the Control Augmentation System (CAS). In particular how yaw, pitch and roll are blended under different flight conditions. In fact, to better help debug the system, we now have the ability to manually toggle each of the three CAS channels off and on (as indicated on the caution and warning panel). The flight characteristic differences are quite dramatic! Before this could happen though, there was a lot of tuning of the center of gravity of the aircraft. This has a huge affect on pitch and takeoff/landing performance. We are now at the stage of tuning the CAS blending to give the DCS Eagle its unique feel based on feedback from our Eagle driver SME and a large number of performance benchmarks. In fact, our F-15 SME had commented that the DCS F-15C has superior flight modeling in many ways to the 3 million dollar trainer. I think many of you will be quite surprised how maneuverable the Eagle can be at slow speeds and high angles of attacks. With the huge rudders, it can perform all sorts of awesome at slow speeds using a lot of rudder input. We've also added separate wheel brake axis this week for the Eagle.
In several ways, this work will act as a foundation for future DCS aircraft AFMs.
As mentioned in an earlier message though, this work has equated to more time and this project will not be ready in time to be released with the 1.2.7 update. However, we think the additional work / time will be well worth the wait.
In regards to AFM, this is how we generally define it:
The aircraft's dynamics are always calculated on the basis of the same physics equations describing translational and rotational motion of a solid body under the influence of external forces and moments disregarding the nature of their origin.
The center-of-gravity can change its location within the speed axis system.
When calculating aerodynamics characteristics, the plane is represented as a combination of airframe components (fuselage, outer wing panel, stabilizer, etc). Separate calculations of aerodynamics characteristics are performed for each of the above named components in the entire range of local angles of attack and sliding (including super-critical), local dynamic pressure and Mach number taking into consideration deviation and grade of destruction of control instruments and some airframe components.
This is the basic definition, but not limited to, what we use to define a DCS aircraft with an AFM. Further detail can be added to include dynamic engine operation, sub-system modeling, fluid dynamics, and damage modeling. None of this must equate to a mouse-clickable cockpit. As such, the definition of an AFM can be a bit broad and encompass products ranging from the the Su-25T to the A-10C.